The human body is configured and muscled to do physical work. Prior to the twentieth century, virtually all physical work was accomplished by human physical activity, supplemented by animal effort guided by the human. Toward the end of the nineteenth century and particularly in the first half the twentieth century, modern machinery has replaced most of the hardest physical work which was previously done by human effort. For example, in the nineteenth century, a plow was pulled by a horse or mule, but a man walked behind controlling the animal through reins and controlling the plow through handlebars. Today's farmer plows from the seat of a tractor. Quite often he has power steering on the tractor so that even that effort is minimized.
The result has been that man does not get enough physical exercise to maintain the optimum condition of the body. The first point of exercise is to work particular muscles so that they are strengthened. The secondary result is that this muscular activity demands increased heart rate to bring nutrients to the muscle and take away the waste products. The lung activity is also increased to remove the carbon dioxide from the blood and oxygenate the blood. This increased respiratory and circulatory activity is also good for the entire body by increasing the circulation. The result of this combination is improved physical condition.
In order to maintain this good physical condition, it would be useful to have a portable exercise device which can be carried with the user so that it is conveniently available when he has the time and desire to do physical exercises.